How to translate 3d-scanned point clouds to .stl format

I scanned a piece with a 3D scanner,and got a set of point clouds.Now I want to triangulate the point cloud with only the patches,I don't want to triangulate the point clouds into tetrahedron,because what I want to get is the surface or the contour of the 3D-model,just like .stl format. Thank you.

[dayseeker]

Hello, i am working on same project, can i ask you how you create stl from point data cloud? I used Delaunay Triangulation but how to use its Connectivity List to make STL, can you please help me?

[Walter Roberson]

dayseeker: note that LIN Hongbin was probably not notified about your question.

Answer 1

[Walter Roberson]

Do you have R2014b or later? If so then see alphashape() and also boundary()

If not then you can find alphashape implementations in the File Exchange.

[LIN Hongbin]

[LIN Hongbin]

this is a 1x1x1 cubic with six midpoinds on six faces,but the rebuild model is not a cubic any more with either alphashape() or boundary().So any other access?

[Walter Roberson]

That looks like a stellated tetrahedron to me, not a cubic.

[LIN Hongbin]

Yes,indeed,it looks like a stellated tetrahedron.But in fact,my point cloud data is a cubic model.the 1st,2nd,3rd column means the x,y,z cooridinate of the 14 points .And point 1 to point 8 makes the 8 vertexes of the cubic,point9 to point14 are the mid point of six faces of the cubic.So I want the remeshed model to be a cubic not the former one looks like a stellated tetrahedron.What should I do ,thank you

[LIN Hongbin]

after delaunay triangulated these points,I got a connectivity of all the points.What can　I do to get the surface triangulation of the rebuilt 3D model.Or,I want to get the connectivities of all the points without inner egdes.Thank you.

[Walter Roberson]

It looks to me as if the stellation arose from using an inappropriate alpha value. The purpose of alpha shapes is to wrap the surface closely around the known data, and the stellated version was a closer wrap, but the amount of wrapping is determined by the alpha values.

I have not used alpha values myself; John D'Errico created an Alpha Shapes File Exchange contribution and would know far more than I would about how to use them.

But keep in mind that you originally said you had a point cloud. Your example here is hardly a point cloud.

[LIN Hongbin]

Thank you !I made a mistake at first that I used boundary without Dedaunay Triangulation.Now I got it.Thank you,Wlter!